Historical Flooding Information

Reports of flooding from November 1917 to May 1998.

October 28-November 19, 1917
Event type: Rain-on-snow flooding.
In the fall, continuous wet and stormy weather caused heavy damage all along the coast, including the Alaska panhandle and the interior.

The Nass Valley flooded to a depth of 10-24 ft. (3-8 m), wiping out the village of Aiyansh. The flooding there was due to a natural logjam. It caused a heavy loss of livestock and property damage. Some of the houses floated away and the residents moved 2 mi. (3.2 km) upstream to Gitlakdamiks (New Aiyansh). The Indian Agent, C.C. Perry, described the situation as follows: “For 66 consecutive days rain storms continued, with devastating winds. Unprecedented Nass River flood did considerable damage to Aiyansh and Gitlakdamiks reserve....” (Perry, diary entry of November 26, 1917). The weather in November had been “... the worst known in 50 years. Floods have been widespread and their effects have been serious in some of the reserves, particularly on the Nass River. The village of Aiyansh has been breached in two places ... all the Indians’ cattle and horses were drowned... the potato crop and hay have been washed away.... Many of the houses were carried away bodily. Gravestones were washed out from the graveyard and piled up with fences and other debris in the village ... at Lak-alzap (Greenville) and at Gwinoha the villages have suffered severely... the three villages will amalgamate and the Nass Indian centre will be Gitlakdamiks where the ground is higher.” (C.C. Perry, letter December 20, 1917). Moeran (1923) described the flood in his biography about James Benjamin McCullagh, minister with the Church Missionary Society at Aiyansh: “September 1917 was an unusually wet month, October was still more so, 16 in. (406.4 mm) having been reckoned as the downfall. Before the melted snow came from the mountains the [Nass] river was already in full spate and absolutely unnavigable.

By the middle of November the river was awful to behold. On the afternoon of Sunday, the 18th, tidings came that the river had broken through near Gitlakdamiks and was rushing down behind Aiyansh.... By Tuesday morning there were over 10 ft. (3 m) of water in the house.... By Wednesday the flood began to show signs of abating... they found the mission house [at Aiyansh] in a deplorable condition ... everything inside was ruined, including the winter’s supply of provisions which had only just been stored. The missionary’s printing office was completely submerged ... his precious books, including the backwoods library, were reduced to a muddy pulp. Some of the other houses in the village had been carried away entirely by the flood. The sawmill and many of the buildings were swept away and the debris scattered all over the country.” In order to avoid future flooding through the breach made in the bank below Gitlakdamiks, it was decided to move the houses from Aiyansh to Gitlakdamiks. In turn each house was pulled down, the lumber carted on sleighs along the Gospel road and rebuilt on a new allotted space. The removal of the mission house was delayed till enough money could be raised for the move. The people suffered much from the cold winter and the lack of proper food, as they had no means of replenishing their potato stock of the barrels and boxes of provisions destroyed or carried away by the flood. When the news of the disaster reached England early in 1918, sympathy and substantial help came from many quarters (Moeran 1923).

November 9-13, 1933
Event type: Rain-on-snow flooding.
Precipitation: Ocean Falls (158.8 mm/2 days), November 9-10, 1933; Aiyansh (161.5 mm/4 days),
High water along the Naas (Nass) River washed away nearly half of the Indian cemetery at Greenville.

May 29-June 3, 1936
Event type: Spring runoff flooding.
Precipitation: Not applicable.
The Nass River started rising on May 29, flooding the northern part of Greenville. The water reached a depth of 5 ft. (1.5 m) over the sidewalks. The sawmill and five houses got flooded. More serious damage may have been done at Aiyansh. The Nass River reached a higher level than the previous record flood of 1917.
Near Aiyansh, the Cranberry bridge and other small bridges were weakened and made unsafe. TheAiyansh district experienced “the worst flood catastrophe the district has ever known.” The water levels exceeded by 8 ft. (2.4 m) anything previously observed. The Nass River started rising on May 29, flooding the northern part of Greenville. The water reached a depth of 5 ft. (1.5 m) over the sidewalks. The sawmill and five houses got flooded. More serious damage may have been done at Aiyansh. The Nass River reached a higher level than the previous record flood of 1917.

Flood damage Aiyansh District: The bank mud sill on Gitzyon Creek bridge washed out letting a corner of the bridge down 1 ft. (30 cm). Three bridges on Tseax Flats floated up. Two of them were tied back into place. The third floated approximately 100 ft. (30 m) down the slough. The Slough bridge on the Aiyansh-Cranberry Trail settled out of place. Two small slides occurred 3 mi. (4.8 km) up the trail. The Cranberry bridge was damaged by drift striking the bridge. Three of the floor beams were knocked out, the stringers were shoved together and half of its decking was gone. The river flat trails were covered with debris. The River Flats were covered with a sticky silt layer 0.5 to 3 in. (1.25 to 7.5 cm) thick and all the potatoes were rotted.

October 4-6, 1936
Event type: Flooding.
Precipitation: Stewart (112.3 mm/2 days), October 4-5, 1936; Aiyansh (46.7 mm/1 day),

May 29-June 3, 1936
Event type: Spring runoff flooding.
Precipitation: Not applicable.
Flood damage Aiyansh District: The bank mud sill on Gitzyon Creek bridge washed out letting a corner of the bridge down 1 ft. (30 cm). Three bridges on Tseax Flats floated up. Two of them were tied back into place. The third floated approximately 100 ft. (30 m) down the slough. The Slough bridge on the Aiyansh-Cranberry Trail settled out of place. Two small slides occurred 3 mi. (4.8 km) up the trail. The Cranberry bridge was damaged by drift striking the bridge. Three of the floor beams were knocked out, the stringers were shoved together and half of its decking was gone. The river flat trails were covered with debris. The River Flats were covered with a sticky silt layer 0.5 to 3 in. (1.25 to 7.5 cm) thick and all the potatoes were rotted.

May 25-June 10, 1948
Event type: Spring runoff flooding.
Precipitation: NA
On June 11, the approaches and stringers of the Aiyansh bridge washed out. The Native Indians were prevented from hauling hay over the bridge until it was fixed.

October 10-14, 1961
Event type: Rain-on-snow flooding.
Precipitation:  October 10-14, 1961; Aiyansh (46.7 mm/1 day),
Nass River flooded, cutting off Greenville and Aiyansh. It was the largest recorded flood on the Nass River. On October 14, the river rose 11 ft. (3.3 m) during the afternoon and evening. The Nass River Water Survey of Canada station near Aiyansh set a record peak stage of 32.22 ft., with a maximum discharge frequency of 1 in 63 years (Meziadin Environmental Advisory Team 1975). In some of the entrenched sections of the river, the water rose about 60 ft. (18 m) above the low water level. On October 15, the Nass River.

Above Shumal Creek recorded a maximum daily discharge of 9,460 m3/s (Environment Canada 1991). On October 16, flash floods ripped through the remote Native Indian fishing villages of Aiyansh and Greenville, leaving more than 100 residents homeless. The heavy rains, coupled with snow-melting warm winds, caused an estimated 20-ft. (6 m) surge in the Nass River. The nearby village of Canyon City, moved to higher ground after a serious flood in 1936, escaped flood damage. According to Jack McFarlane, district superintendent of Indian Affairs, who flew over the stricken area, debris from Aiyansh was scattered 2 mi. (3.2 km) downstream. He said 15% of the village of 500 was destroyed, and another 65% heavily damaged. Most of the village flooded with water up to 12 ft. (3.6 m). Fourteen homes were swept away and 17 others damaged. Two schools and two churches served as temporary accommodation for the about 100 homeless residents. Over 70 other buildings, including two schools and the Indian Health Services Station were badly damaged. *1) Floodwaters left more than 6 in. (15 cm) of silt in one of the schools.

In Greenville, 25 mi. (40 km) downstream from Aiyansh, three houses were lifted off their foundations. Sixty homes were flooded, but escaped destruction because they were built on pilings 3 ft. (90 cm) above the ground. At the crest of the flood, about two-thirds of Greenville was under water. In Greenville the school was closed. The school, which is on high ground, was used to house evacuated residents. The village wharf was swept away and the bridge to the sawmill washed out. Much of Greenville’s winter supply of fish and meat was lost. The Greenville- Canyon City road was completely under water. According to R.C. Telford, manager for the Columbia Cellulose woods division, logging roads connecting Terrace with the villages washed out. The logging company ferried 2 tons of blankets and clothing, donated by the citizens of Terrace, across the Nass River to Aiyansh. L.S. Hewer, B.C. Commissioner for the Red Cross Society, arranged help in event of a food shortage among the flood victims of the Nass area.

The log drive on the Lower Nass River suffered heavy losses because a large amount of logs ended up in the ocean. At Stony Point, a Can Cel crane-shovel was flooded, sustaining $40,000 damage. The bridge across Ginluklak Slough, west of Greenville on the south bank of the Nass River, floated off its pilings. The complete bridge, including stringers, ended up downstream near Kincolith. A large section of the bridge was towed back with a tug. Efforts to put it back into place failed after the water levels had receded. The bridge under construction across the Kiteen River, below the junction with the Cranberry River, washed away. Construction on the 180-ft. (54 m) long bridge, including approach work, had started at the end of September. Because the bridge was built using a skidrig piledriver, false work was required every 16 ft. (4.8 m) to support the sleigh. When the water levels rose, there was no room for drift. With the exception of a few pilings near the shore, everything was washed away. One of the stringers ended up on the porch of the new school at Aiyansh, which was built on an old river channel (J. Wright, pers. comm.). *2)

*1) The village of Aiyansh, partially devastated by the flood of October 1961, was again relocated. In a secret ballot, 102 residents voted for, and 3 against, relocation. A tentative site was selected on higher ground south of the river (John M. McFarlane, Indian Affairs Branch, Terrace). This third settlement of Aiyansh is called New Aiyansh.
*2) The original settlement of Old Aiyansh was built on a site approximately 3 mi. (4.8 km) away at the foot of a back channel parallel to the main river. After the 1917 flood it was moved to a new location. Some of the buildings were cut in sections and moved on rollers using manpower and horses. After moving them through an old back channel, which had to be cleared of brush, they were rebuilt on higher ground. Some of the buildings, including the school, were built on an old back channel (J. Wright, pers. comm.).

June 8-15, 1964
Event type: Spring runoff flooding.
The Nass River rose at a rate of 1.5 ft. (45 cm) a day. Residents of the Native Indian villages in the Nass River area also stood by for evacuations. At the height of the flood, some residents of Telkwa had to be evacuated.

October 16-20, 1964
Event type: Flooding.
Aiyansh (111.5 mm/2 days), October 18-19,
During the night of October 21, partial flooding was reported from two Native Indian villages on the Nass River. Heavy rains caused a sudden rise on the Nass River as it approached the 1961 flood level. The Aiyansh Indian village got flooded. The Senior Indian School was flooded and the teacherage trailer washed away. Animals and personal belongings were moved to higher ground.

October 5-9, 1974
Event type: Flooding and debris slides.
(103.9 mm/2 days), October 7-8, 1974; Nass Camp (115.3 mm/2 days), October 7-8, 1974;
The freezing level in the mountain basins of the Skeena and Nass rivers was down at 2,500 ft. (750 m), a heavy snowpack was forming (Meziadin Environmental Advisory Team 1975). High river levels and several washouts in the Bell-Irving area closed Cassiar Highway 37 from Kitwanga to Bob Quinn Lake. Bridges in the Nass River valley flooded or washed out. Numerous washouts and slides closed the Stewart-Meziadin road. Bitter Creek bridge was damaged and had to be reconstructed. Minor flooding occurred in Kitsault and Alice Arm. At Alice Arm, 60 mi. (96 km) northeast of Prince Rupert, several houses and many unoccupied shacks were washed away. The Nass Road was reported washed out in two locations.

Nass Camp flooded and the entire Nass area was without power. A mudslide took out a transmission tower at the south end of Lava Lake. There was flooding and road grade erosion along the South Seaskinnish Creek near Nass Camp. Numerous grade washouts occurred in the Nass Valley as far north as Meziadin Lake.
Floods caused by the heavy rain isolated Native Indian villages and logging camps along the Nass River. On October 9, the Nass River above Shumal Creek recorded an estimated maximum instantaneous discharge of 8,920 m3/s and a maximum daily discharge of 7,670 m3/s. The instantaneous discharge was an all-time high for the period of record (Environment Canada 1991). The Nass River flooded homes in the Nisga’a village of Greenville. New Aiyansh, another Nisga’a village, was isolated for several days by road closures. *1) Flooding and washouts also isolated the Twin River Timber Ltd. base of Nass Camp.

*1) The Nisga’a population numbers about 6,000. About 2,500 of these live in the Nisga’a villages of Gingolx (Kincolith), Lakalzap (Greenville); Gitwinksihlkw (Canyon City) and Gitlakdamiks (New Aiyansh). The rest live elsewhere in Canada.

October 13-16, 1974
Event type: Flooding and debris slides.
Aiyansh (82.0 mm/2 days), October 14-15, 1974;
Between October 13-15, Prince Rupert recorded 4.33 in. (110 mm) of rain. *1) On October 14-15, the Terrace airport recorded 3.23 in. (82.0 mm) of rain in 24 hours, setting a record for October. Precipitation measured in the 24-hour period starting 6 p.m. on October 14 at the Kitimat Fire Hall, amounted to 4.52 in. (114.8 mm). In the Nass and Skeena River valleys, the freezing level rose to 12,000 ft. (3,600 m), melting the heavy snowpack that formed during early October (Meziadin Environmental Advisory Team 1975). Combined with the record rainfall on October 14-15, this caused major flooding on most of the rivers in the area. The Skeena River basin was located mainly outside the region of intense precipitation.

The Nass River rose to record heights. The WSC station near Aiyansh recorded a peak stage of 31.34 ft. At Moore Creek, about 9 km. downstream from the confluence with the Meziadin River, the water level rose 45 ft. (13.5 m) above spring low water level and flooded the highway. About 7 km downstream from the confluence with the Bell-Irving River, just upstream from a 60-ft. (18 m) wide canyon, driftwood was deposited at an estimated elevation of 85 ft. (25.5 m) above the low water level. The road grade and culverts on the east side of Lava Lake sustained extensive damage.

October 29-November 1, 1978
Event type: Flooding and debris slides.
Aiyansh (177.4 mm/3 days), October 30-November 1,
On October 31, Terrace recorded 114.8 mm of rain in 24 hours, setting an all time record any time of the year, with 70-80 km/h winds. On November 1, another 89.1 mm of rain fell in a 24-hour period. The storm appears to have centered around the Terrace-Kitimat area. It originated in a trough of another “low” which was dissipating over Siberia. Before the storm there was little accumulation of snow below the 1,000 m elevation.

The bulk of the storm’s rainfall resulted from the passage of two frontal waves under a strong southwestern flow of warm moist air aloft. Sandspit airport recorded the largest two-day storm with 120.3 mm. An estimate of the frequency of the multi-day event based on 30 years of records from Sandspit airport is between 75-95 years (Schaefer, 1979a). Sewell Inlet recorded a total rainfall of 879.3 mm for the month of October, and 1,132.2 mm for the period October 1-November 5.

The Atmospheric Environment Service concluded that snow melt did not likely play an important role in this event (Schaefer 1979b). Snowmelt at higher elevations, however, is believed to have contributed to this event. According the weather specialist at the Terrace airport Harry Earle, the flooding was triggered by heavy rain and high freezing levels resulting in snowmelt in the mountains. (Terrace Standard, October 7?, 1992). Flows on the coastal streams peaked on November 1.

Roads along the Nass River washed out. In Greenville, a small tributary to the Nass River jumped its bank, causing damage to a gymnasium and cemetery. Rosswood and Cedarvale were without road access. At Rosswood, a torrent of water ripped across the highway, taking out a bridge and sweeping away a new home. The house was moved some 150 ft. (45 m) off its foundations. Greenville was isolated for more than a week. It took 10 days to make the final road repairs. On November 2, the Greenville water supply was hit by a mudslide, making the water muddy and reducing the pressure. The road at Kaseaden Camp, 12 mi. (19.2 km) north of Greenville was washed out. Helicopter relief flights to outlying communities were grounded by poor visibility. Because of the closure of Highway 16, the mail destined for Alaska was returned to Seattle. From there it was sent on the Alaska State Ferry.

November 28-December 8, 1990
Event type: Storm surge and tidal flooding.
1990; Nass Camp (152.0 mm/5 days), December 2-6,
According to John Newhouse, Ministry of Highways District Manager, two days of hauling riprap saved the highway. The road between New Aiyansh-Greenville was closed by a slide and flooding of the Nass River.

October 6-14, 1991
Event type: Flooding and landslides.
Nass Camp (142.0 mm/3 days),
Record rainfall also caused drainage problems throughout the Nass Valley. Approximately 360 mm of rain fell in seven days, equaling the monthly average for the region. The flooding in the Nass Valley was described as the “worst since October 1961” (British Columbia Report). *3) In some areas the roads were under more than 1 m of water. Because of flooding along Kitsumkalum and Lava Lake, the road north of Terrace from Dover Road to Greenville was closed. The Nisga’a Highway was flooded at Lava Lake. The Ministry of Forests confirmed that extensive damage was done to the road north of Nass Camp, isolating nearly 3,000 Nass Valley residents in Nass Camp, Greenville, Canyon City, and New Aiyansh. Fresh food was airlifted to the trapped residents by helicopter through the Provincial Emergency Program (PEP). In the largest airlift in PEP’s history, nearly $25,000 worth of groceries was airlifted. A total of 14 flights were made, during which mail and ballots for the provincial election were also delivered. Ministry of Highways officials reported that more than 80% of a 22-km road to Greenville was completely under water.

Many washouts occurred, bridge structures were damaged, and other bridges had their approaches washed out. The Ministry of Highways district manager estimated damages to the roads in the Nass Valley to be approximately $500,000. On October 23, the road to Greenville was reported open to traffic. The more than 800 residents of Greenville had been isolated since October 9. A contractor working into the night saved a major bridge over the Cedar River. At one point the level of the Cedar River rose 3 ft. (90 cm) in 15 minutes. In the Kispiox Valley near Hazelton heavy damage to fish eggs was reported. Floodwaters in the Nass River may have wiped out more than half of the salmon eggs already laid that year. The main species affected were pink, chum, and sockeye salmon, spawning in August and September. (Les Jantz, Dept. of Fisheries and Oceans In: Prince Rupert Today).

*3) According to Lakalzap band administrator Wallace Clark, the Nass River levels were higher than during the record flood in 1961. The Nisga’a Tribal Council continued to press demands for an audit of logging practices in the Nass Valley to see how clearcut logging had contributed to the flooding.

May 27-28, 1998
Event type: Spring runoff flooding.
Precipitation: Not applicable.
Flooding was reported from the Nass Valley between Terrace-New Aiyansh. Flooding overnight May 27-28 at Beaver Flats cut off access to Lachkaltsap Reserve (Greenville). By May 29, the flooding had worsened. Between 7- 8 km of road into Greenville flooded. *1)

*1) Residents demanded significant action to end the annual flooding of the road when runoff swells the Nass River. According to regional highways director Dirk Nyland, the solution would cost perhaps $10 million. He noted, “There’s no temporary fix in the meantime. We just can’t raise the road; we would to have to move it over and that would mean moving all the power poles. As well, the road runs along coho (salmon) habitat requiring extra care and expense when doing any kind of road construction.” (The Terrace Standard, June 3, 1998).

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